[Easy][FSDP] Minor doc fixes (#74214)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/74214
Test Plan: Imported from OSS
Reviewed By: saketh-are
Differential Revision: D35045122
Pulled By: awgu
fbshipit-source-id: 701181cfdb93cb4ebf8e036a9f5c118f38005d6d
(cherry picked from commit b6b4c64f82d0b053aa75ee74a28fffa53cf87880)
